Compared with conventional rotational symmetric surfaces, a freeform surface has larger degrees of freedom, which can accurately control light path. In recent years, freeform surfaces have been successfully used in illumination system, which can obtain a better illumination effect and a compact structure.
However, the conventional illumination system with freeform surface is designed for a single light source. The light source is unique and immovable. When the single light source is moved or other light sources are introduced, illumination effect of the illumination system with freeform surface is decreased.
What is needed, therefore, is to provide an illumination system with freeform surface, which can overcome the shortcomings as described above.